Current-collectin gbrush



Dec. 16,1930. c. HANSEN ET AL I 5 i CURRENT COLLECTING BRUSH Filed July 22, 1924 Patented Dec. 16, 1930 UNITED STATES PATENT comer.

CHARLES HANSEN AND HORACE S. ELLSON', OF LAKEWOU D, OHIO, ASSIGNORS 'IO NATIONAL CARBON COMPANY, INC., A CORPORATION OF NEW YORK CURRENT-COLLECTING BRUSH Application filed July 22, 1924. Serial No. 727,519.

This invention relates to current collecting brushes for dynamo electric machines, and more particularly to improved means for mechanically and electrically connecting conductors to such brushes.

In securing the usual flexible copper conductor or cable, known as a shunt or pigtail, to a current collecting or distributing brush block of carbon, graphite, metalgraphite or other brush composition, it is highly desirable that the electrical'resistance or contact drop of the connection shall be as low as possible andthat the connection shall be mechanically adequate to withstand excessive vibration and other severe service conditions.

Heretofore, such conductors have been variously secured to brushes, as by means of bolt and nut fastenings, hollow rivets, wedge devices, and soldering, but these connections have not proven entirely satisfactory for all types of brushes, especially those made for high current densities, because of their relatively high contact drop and because of their tendency to loosen under service conditions to which they are subjected.

The primary object of this invention is therefore to provide a current collecting or distributing brush, comprising carbonaceous material such'as carbon, graphite and the like, having a conductor that is adequately connected, both mechanically and electrically, to the brush block. The above and other objects and the novel features of this invention will be apparent from the following specification taken with the accompanying drawings, in which Figs. 1, 2, and 3 are perspective views illustrating brushes embodying the present invention;

Fig. l is a vertical sectional View of the brush, taken on the line 4-4 of Fig. 1, showing a portion of a brush holder therefor;

Fig. 5 is a similar vertical sectional View illustrating a modification; and

Fig. 6 is a transverse sectional View taken on the line 66 of Fig. 1.

Referring to Figs. 1, 4; and 6 particularly, as illustrated, the brush block B may consist of a rectangular prism of carbon,.

graphite, metal-graphite, or other suitable brush composition, the outer or rear end of the brush being molded or otherwise formed of a smaller section, opposite sides thereof offset inwardly to provide parallel faces 10, 10, and shoulders 11, 11. The four longitudinal corners of the brush are also molded or otherwise formed with removed or cutaway parts, as at 12, to leave triangular or equivalent spaces at the rear corners of the brush block parallel to the main axis of the brush, for a purpose to be described. One or more, desirably three, parallel holes H are drilled or otherwise formed through the rear end of the block B, terminating in the faces 10, 10, and are designed to receive fastening devices by means of which one or more conductors are secured thereto. The reduced end of a brush block of carbon or graphite is desirably electroplated or otherwise coated with copper or other good conducting material, such coating also covering the surfaces of the walls of the holes H through the block.

Each brush may have one or more flexible conductors C mechanically and electrically connected to it. As illustrated in Fig. 1, a conductor is connected at each of the four rear corners of the brush block B, and the outer ends of these conductors may be connected in pairs to suitable terminal lugs L. Other arrangements of the conductors and terminal lugs may be provided.

The brush end of each of the conductors C is secured to a plate P which in turn is secured to the brush block B. As illustrated in Fig. 1, twoplates are employed for securing the four. conductors to thebrush bloclgsuch plates P and P bearing respectively against the faces 10 and 10 and resting on the shoulders 11, 11. These plates are of metal, desirably of relatively stiff sheet copper, and the opposite ends thereof are bent upon themselves as at E to provide a substantially triangular or equivalent recess R at each end of the plate for receiving and gripping the brush end of a conductor. The plate ends are bent around the conductors to compress and grip the conductor ,ends and, in addition, a bead 15 may be forced into the wall of the reversely bent plate end to provide a better mechanical and electrical connection between the conductor and plate. The conductor ends desirably substantially fill the recesses R and are desirably also soldered therein to improve the electrical and mechanical connection.

The plates P, P are relatively narrow and substantially cover the faces 10, 10 to reinforce the reduced end of the brush block. Between their reversely bent ends, the con nection plates P, P are apertured toprovide one or more holes 16 corres 'ionding in size and location to those in the brush block 13 so that when plates are assembled imposition on the brush block with their reversely bent ends occupying the spaces at the cut-away corner parts of the brush block, the holes 16 therein will register with the holes H that extend through the brush block.

The plates P, P are preferably secured in position on the brush block by means of solid one-piece cylindrical metal rivets S filling the registering holes in said block and plates and having enlargements or'heads S at their ends bearing against the outer surfaces of the plates and holding the plates'firmly in contact with the faces 10, 10 of the brush block. These rivets are of ductile metal, such as copper, and desirably of a diameter to closely [it the holes in the plates and brush block. After assembling the blocks and conductorcarrying plates with their holes in registry and inserting the copper rivet blanks in such registering holes, the outer ends of the rivet blanks are upset or enlarged by a device, such as a vertical airhammer, which turns over the rivet ends and forms the solid integral heads S by a process of percussion or hammering consisting in a successive number of rapid comparatively light blows against the end of each rivet, whereby the heads S are formed and simultaneously the ductile rivet material between the heads is forced back and expanded in the holes in the carbon brush and plates to fill them eompletelyso that there is no play between such holes and the rivets. This expansion of the solid rivet, however slight, serves to force the body of the rivet into intimate contact with the plain or electroplated walls of the holes in the brush block, as well as the holes in the plates, and thereby substantially reduces the contact drop of the connection. In fact, it has been found by experiment that the contact drop of a solid filling-rivet connection according to this invention is lower than a connection employing a hollow tubular rivet of well known form in the same relation. The same advantage of reduction in contact drop is derived by the use of solid filling rivets in similar brushes employing metal-graphite or other metallic composition not requiring a metallic or copper coating in the holes and adjoining parts of the brush. The solid rivet expanded as indicated also provides a superior mechani cal connection and the side plates serve to substantially reinforce the apertured rear end of the brush to which the conductors are connected.

As illustrated in Fig. l, the heads of the rivets do not project beyond the outline of tl 1c larger section of the brush block 15, and are desirably substantially flush with the faces of the brush block that engage the brush holder so as to assist in guiding the brush in its holder, especially when the brush becomes shortened by wear.

Fig. 5 illustrates a slight modification, in which the outer faces of the plates are sul stantially flush with the main faces of the brush block, and the holes in such plates are tapered, as at 18, to receive the swaged ends or heads S of the solid filling rivets, the outer ends of such heads thereby being substantially flush with such plates and the faces of the brush block. Either or both of such swaged solid rivet heads may of course be formed by pressing or hammering the solid filling rivet blanks axially, as previously in dicated, to enlarge the ends of the blanks into the holes in the plates and simultaneously expand the rivet material between the heads to fill the rivet material into all irregularities in the holes of the brush block and provide more intimate contact between the brush and plates and the rivets.

It is desirable to have a metal wearing surface at the rear end of the brush for the usual pressure device or spring on the brush holder that holds the brush against a commutator or collector ring. Such wearing surface may be provided, as illustrated in Fig. 1, by a tongue T formed integral with one of the plates, P, and bent perpendicular from the medial portion of such plate so as to overlie and de sirably contact the central part of the rear end of the brush block B. It is also desirable to provide means on the brush for lifting it out of the brush holder guide or otherwise adjusting it therein. For this purpose, as illustrated in Fig. 1, one of the plates, P, may be provided with an upwardly and rearwardly extending tongue U formed integral with this plate and projecting from its medial portion. I

The wearing tongue and lifting tongue may beportions of plates that are separate from the connection plates P, P, as illustrated in Fig. 2. Here, each of the connection plates is provided with only one reversely bent end,

luu

such ends fitting in diagonally opposite spaces 12 at the cut-away corners of the brush block. These bent ends grip the brush ends of a pair of conductors G united at their outer ends to a single terminal lug L. An additional copper plate W carrying an integral central tongue W bent to closely overlie the rear end of the brush may be positioned to bear against the outer face of one of the connection plates, P, and a second additional plate X, preferably of stiller material such as sheet iron, and provided with an upwardly and forwardly extending lifting tongue X parallel to but spaced from the bearing tongue may bear against the outer face of the other connection. plate 1 The four plates, assembled in posi tion with their holes in registry with those of the brush block, are then mechanically and electrically connected to the brush block by a number of solid one-piece copper rivets in the manner already described.

The bearing plate as well as the lifting tongue may be parts of the same connection or supplemental plate. As shown in Fig. 3 for example, an integral medial part of one of the connection plates may be bent so as to provide a portion Y that will closely overlie the rear end of the brush block, and an extension of this portion is bent upwardly and over the bearing portion to provide a lifting tongue Y spaced from the bearing portion Y. Other wise the construction shown in Fig. 3 is in all essential respects similar to those already described.

Although the improvements are shown and described in detail, it will be understood that numerous changes may be made in the forms disclosed, without departing from the inventions or sacrificing any advantages thereof.

We claim: 7

1. A current-collecting brush comprising a block containing carbon or graphite and having part of one of its longitudinal corners removed at the outer end of the block, a flexible conductor, a plate bearing against said lock and having one end thereof bent upon itself to clamp an end of said conductor, said bent end and conductor end therein being disposed in the space corresponding to said removed part of said block and extending substantially parallel to the main axis of the brush and transversely of the length of said plate, and means securing said plate to said block.

2. A current-collecting brush comprising a block containing carbon or graphite and having one of its longitudinal corners partially removed adjacent the outer end thereof, a flexible conductor, a plate bearing against a face of said block adjacent its outer end and having a tongue overlying the outer end of said block, said plate also having an end bent upon itself to grip an end of said conductor and lying in the space corresponding to said removed corner part, and means mechanically and electrically connecting said plateto said block.

3. A current-collecting brush comprising a block containing carbon or graphite and having longitudinal corners partially removed at the outer ends thereof, flexible conductors, a plate bearing against said block and having its opposite ends bent upon itself to grip ends of said conductors, said bent ends of the plate and the conductors gripped thereby lying in the spaces provided by said removed corner parts, and means for me chanically and electrically connecting said plate to said block.

4. A currentcollecting brush comprising a block of carbon or graphite having parallel longitudinal corners cut-away at their outer ends and one or more holes extending through said block between said cut-away corners, conductors, plate means bearing against said block and having reversely bent ends gripping said conductors and occupying the spaces left by said cut-away corners, said plate means having one or more holes registering with the holes in said block, and fastening means extending through said holes to mechanically and electrically connect said plate means and conductors to said block.

5. A current-collecting brush comprising a substantially rectangular prismatic block of carbon or graphite having longitudinal corners partially removed at their outer ends, conductors, plates bearing against opposite faces of said block and having ends thereof bent upon themselves to grip ends of said conductors and disposed in the spaces left by such removed corner portions, one of said plates having a tongue overlying the outer end of said block, and means for mechanically and electrically connecting said plates and conductors to said block.

6. A current-collecting brush comprising a block of carbon or graphite having longitudinal corners cut-away near the outer end of the block and holes extending through said block between said cutaway corners, flexible conductors, plates bearing against the opposite faces of said block and having holes registering with the holes in said block, said plates having ends bent upon themselves and secured to the ends of said conductors, one of said plates having a tongue overlying the outer end of said block and the other of said plates having a lifting tongue, and members extending through said registering openin s in the plates and block for mechanically and electrically connecting said plates and conductors to said block.

7 A current-collecting brush comprising a block containing a substantial amount of carbon or graphite, such block having offset faces at one end providing a reduced section, holes extending through said section and terminating in said faces, corners of said section being removed leaving corresponding spaces; plates bearing against said faces and having holes registering with the holes in said block; flexible conductors having inner ends disposed in said spaces and secured to said plates and outer ends secured together; and solid metallic rivets filling said registering holes in said block and plates and mechanically and electrically securing said plates and conductors to said block.

In testimony whereof, We aflix our signatures.

CHARLES HANSEIQ. HORACE S. ELLSON. 

